Remove broken link from C29 (#3700)

This link no longer exists. The domain itself still has a site on it and
I looked for the specific post, it seems to have been removed.


[Preview](https://deploy-preview-3700--wcag2.netlify.app/techniques/css/c29#resources)

Co-authored-by: Patrick H. Lauke <redux@splintered.co.uk>

Author: hidde-logius

techniques/css/C29.html

@@ -362,13 +362,7 @@ <h2>Related Techniques</h2>
 	</section>
 	<section id="resources">
 		<h2>Resources</h2>
-		
-		<ul>
-			<li>
-				<a href="http://www.456bereastreet.com/archive/200608/build_your_own_php_style_sheet_switcher/">Build your own PHP style sheet switcher</a>
-			</li>
-		</ul>
-		
+				
 		<section>
 			<h3>Using cookies</h3>
 			<p>A user's selection can be made persistent across pages, and from one visit to another, by storing information on the user's computer via a cookie. This functionality requires cookies to be supported by and allowed on the user's computer. Cookies can be created, read, modified and erased by using client-side scripts, such as Javascript, or by server-side scripts, such as CGI scripts. Reliance on client-side technologies will require the support and availability of the technology on the user's computer in addition to supporting and allowing cookies. </p>
@@ -408,4 +402,4 @@ <h3>Progressive Enhancement and Unobtrusive Javascript</h3>
 		</section>
 	</section>
 </body>
-</html>
+</html>